jeffrey brown looks into that. >> brown: the question after the events of last week: how safe can we ever be? especially in major cities. thousands of people gathered in public buildings or for big events. it's a question that was posed after the 1995 oklahoma city bombing that killed 168. and a year later, after a pipe bomb exploded in atlanta's centennial olympic park during the summer games, killing one and injuring 111. 9/11, of course, brought a ratcheting up of security measures including among much else, the creation of the department of homeland security and the t.s.a. and surveillance cameras watching for suspicious activities. and there have been examples of thwarted attacks on public spaces, notably in 2010. the car bomb in new york city's time square was disabled after two street vendors reported the smoking vehicle to police. since 2003, homeland security's urban area security initiative grants have funneled billions of dollars to major cities for anti-terrorism training and equipment. security experts will now study boston for lessons learned for future public gathering